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484 Lubricant Additives: Chemistry and Applications
Reaction products of P
2
S
5
with terpenes (dipentene, pentene), polybutenes, ole ns, and unsatu-
rated esters belong to the same group; among these, the terpene and polybutene products have been
proposed for crankcase oils. Metal dialkyldithiophosphates serve at the same time as detergents, EP
additives, and anticorrosion agents, when the corrosion is caused by oxidation products; in this case,
the metal is protected from attack by organic acids by the formation of sul de or phosphate lms.
2,5-Dimercaptothiadiazole derivatives have a similar effect.
19.5.9 ANTIOXIDANT SELECTION, SYNERGISM, AND TESTING
Most of the crankcase engine antioxidant needs are met by the ZDDP. Today’s higher-temperature
engines (Table 19.8) require supplemental ashless antioxidants to pass the Sequence IIIE engine.
Therefore, modern engine oils use three or more different types of antioxidants, with the highest
level (0.1–0.15 wt%) being the ZDDP.
The previous generation engine to measure lubricant oxidation was the Sequence IIID, which
required a maximum oil kinematic viscosity increase of 375 cSt at 80 h of operation. A fail result
is shown for the base formulation at less than half way through the test (30 h). Addition of 0.5 wt%
arylamine antioxidant to base formulation results in easily meeting the kinematic viscosity increase
requirement. The same pass result could be obtained by increasing the ZDDP level, but the current
limits on phosphorus level prevent this option.
Another important antioxidant phenomenon is known as inhibitor synergism. Another way of
stating the de nition shown here is “1/2 (or partial) levels of two compounds produces a greater ben-
e t than a full level of either alone.” Synergistic combinations of inhibitors can extend a lubricant’s
temperature and use ranges thereby boosting its performance.
Either formulations containing 0.5 wt% of alkylphenol (rating = 63) or 0.5 wt% of arylamine
as inhibitor (rating = 60) alone do not provide a suf cient deposit control to pass this test. However,
a mixture of two inhibitors at 0.25 wt% each offered an outstanding rating, 71, which is a pass
result.
The ef ciency of antioxidants in lubricating oils is tested on the laboratory scale in a battery of
bench tests and engine tests under more severe conditions. This is particularly true for motor oils,
where only the practical test in the engine can assess, for instance, the high-temperature ef ciency
of dithiophosphates and the frequently antagonistic effects of dispersants and oxidation inhibitors
in a given additive combination.
As a rule, however, the nal formulations of products are subjected to time-consuming eld
testing.
TABLE 19.8
Approximate Temperature of Internal Surfaces in a V-8 Engine
Area of Engine Temperature Range (
o
C)
Exhaust valve head 650–730
Exhaust valve stem 635–675
Combustion chamber gases 2300–2500
Combustion chamber wall 204–260
Piston crown 204–426
Piston rings 149–315
Piston (wrist) pin 120–230
Piston skirt 93–204
Top cylinder wall 93–371
Bottom cylinder wall Up to 149
Main bearings Up to 177
Connecting rod bearings 93–204
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Additives for Crankcase Lubricant Applications 485
Some screen and engine oxidation performance tests are as follows
The ASTM D-943 or turbine oil oxidation test is used for hydraulic oils. In this screen,
molecular oxygen is blown through a quart of the oil at 95ºC containing an iron and copper
coil. The time taken to reach an oil TAN of 2 are recorded, with a pass result considered to
be anywhere from 1000 to 3000 h, depending on the speci c customer approval.
The ASTM D-2272 (rotary bomb oxidation test [RBOT]) and ASTM D-4742 (thin- lm oxygen
uptake test [TFOUT]) are two other industry-recognized bench tests. These screens use
pressure to accelerate the oxidation process to simulate the lubricant’s extended service
or “real-world” conditions. The RBOT also nds utility for formulating industrial oils,
whereas the TFOUT is used to measure the oxidation performance of passenger car and
heavy-duty diesel engine oils.
Indiana stirred oxidation test (ISOT) has several versions, with temperature ranging from 150
to 165ºC. The beaker of oil is stirred vigorously for 24 h in the presence of iron and copper
catalysts. Measurements include the oil’s kinematic viscosity increase, TAN built up, and
amount of pentane insoluble sludge generated.
Pressure differential scanning of calorimetry (PDSC) is designed to predict the improvement
inhibitors add to an oil of poor oxidative stability.
Passenger car motor oil (PCMO) engines for oxidation performance consist of
The Sequence IIIE and Sequence IIIF to measure an oil’s viscosity built up
The Sequence VE and Sequence VG to measure sludge control (Table 19.3)
The extreme temperature ranges reached in Sequence VE engine are given in Table 19.8. The oil
bulk temperature does not reach these high temperatures, but the uid operates in proximity of
these parts. Since the oxidation process is accelerated by temperature, one can see why an oil’s
antioxidant system must be specially designed to be effective.
Typical passenger engine design has been undergoing dramatic changes since it has been
introduced to the public in the early 1920s.
Table 19.9 summarizes several major design/ uid system changes observed. The two critical
parameters affecting lubricant stability and projected life are
1. The large increase in the engine oil temperature (2×)
2. Steady decrease in the amount of lubricant (~5×)
These two factors have put extra demands on the lubricant’s antioxidant system, whereas somewhat
recent limits on phosphorus level have “capped” the use of ZDDP.
•
•
TABLE 19.9
Changes in the V-8 Engine over Past Seven Decades
1920 1960 1990
Engine capacity (L) 6 2 1.6
Brake horse power 50 70 130
Engine speed (rpm) 1200 5000 7000
Oil temperature (°C/°F) 60/140 90/194 130/266
Oil capacity (L) 14 4.5 3.5
Valve train Side valves Push rod, overhead valves Twin overhead camshafts four valves
Fueling system Single-choke carburetor Multichoke carburetor Fuel injected
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486 Lubricant Additives: Chemistry and Applications
19.6 VISCOSITY MODIFIERS
19.6.1 I
NTRODUCTION
VMs are added to a lubricant formulation to reduce the viscosity–temperature dependence of
the base oils. This class of lubricant additives is the technology that enabled the development of
multigrade lubricants in the 1960s. The primary feature of multigrades is that they allow the engine
to start at low temperatures while providing suf cient viscosity at elevated temperatures to protect
the engine against wear.
A lubricant oil formulation based on a group I mineral base stock without a VM additive will
have a limited range of temperature operation since it has a relatively strong viscosity–temperature
relationship. VMs are oil-soluble polymers that, when added to a base oil and additive mixture, will
thicken the mixture at high temperatures while having a minimal thickening effect at lower tem-
peratures (Figure 19.31). A very simpli ed mechanism to explain this phenomenon would be that
the polymer–oil interaction at low temperature is minimal but increases as the temperature rises.
This interaction of the polymer with the base oil at elevated temperatures increases the effective
hydrodynamic volume of the polymer thereby increasing the effective volume fraction of the VM.
This, in turn, leads to an increase in lubricant viscosity. To make use of this phenomenon, a low-
viscosity base oil mix is used to which the VM and additive mixture is added. The low- viscosity
base oils permit the oil to ow freely at low temperatures, whereas the VM increases the viscosity
at higher temperatures.
19.6.2 VISCOSITY MODIFIER TYPES
There are several types of VMs available to the oil formulator. Each of these has strengths and
weaknesses. Therefore, it is sensible to select the correct type for the intended application. Table 19.10
details some of the most common VMs in use today.
OCPs are prepared by either Ziegler–Natta or metallocene catalysis. Besides containing ethyl-
ene and propylene, diene monomers may be added to improve the handling characteristics of the
solid form of the polymer. The relative amounts of each monomer will dictate the solubility of the
copolymer. As the level of ethylene in the copolymer increases, polymer solubility decreases esp-
ecially at low temperatures. This effect at low temperatures has the bene cial effect of lowering the
polymer contribution to subambient viscosity. But one must be careful not to go too far because,
at very high ethylene contents, the OCP will drop out of solution or form gels at low tempera-
ture. This may only manifest itself after several month storage at low temperatures. The monomer
sequence distribution is also critical and can be carefully controlled to maximize the amount of
ethylene in the copolymer and hence give minimal low-temperature thickening. OCPs are the most
popular type of VM in use today due to their high thickening ef ciency and relatively low cost.
Base oil + viscosity modifier
Base oil
log-log viscosity
log temperature
FIGURE 19.31 Effect of VM on base oil viscosity–temperature dependence.
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Additives for Crankcase Lubricant Applications 487
Styrene–diene copolymers are prepared by an anionic polymerization of styrene with either
butadiene or isoprene. The residual unsaturation in the backbone is removed by hydrogenation.
Tapered block copolymers are prepared by charging both monomers together at the beginning of
the reaction. To synthesize A-B block copolymers, the monomers are added sequentially. Anionic
polymerization yields polymers with very narrow molecular weight distributions especially when
compared with those of OCPs and PMAs. A narrow molecular weight distribution yields the
maximum shear stability to thickening ef ciency ratio for a linear polymer. Because styrene–diene
copolymers also possess excellent low-temperature properties and good thickening ef ciency, they
have found widespread use in engine oils. One of the few drawbacks is that, relative to OCPs, they
are relatively expensive to make due to the two-stage synthesis process and more expensive starting
materials. Another issue is that A-B block copolymers undergo more temporary viscosity loss under
high-temperature, high-shear-rate (HTHS) conditions (such as in lubricated journal bearings),
especially when compared to OCPs.
Star polymers are prepared by an “arms- rst” process whereby isoprene (and an optional
comonomer) is anionically polymerized to a predetermined molecular weight. The arms are then
linked together by adding divinylbenzene that forms an ill-de ned gel core. The number of arms per
star is de ned by the amount of divinylbenzene relative to the polymer arm concentration. Finally,
the star polymer is hydrogenated. These polymers have exceptional low-temperature properties but
undergo more permanent viscosity loss under severe operating conditions when compared to OCPs
at the same nominal shear stability index (SSI).
PMAs are prepared by free-radical polymerization of alkylmethacrylate monomers. This
produces a polymer with a relatively broad molecular weight distribution. To reduce molecular
weight and hence increase shear stability of the polymer, the initiator concentration is increased.
In addition, a chain transfer agent may be added during the polymerization process. This stops
the polymer chains from growing and enables the production of a polymer with low molecular
weight and exceptional shear stability. The composition of the monomers in the polymer backbone
is chosen to optimize low-temperature properties viscosity index (VI) and thickening ef ciency.
PMAs are frequently used because of their exceptional low-temperature viscometric properties.
Because of this, they are used extensively as VMs in gear oils, automatic transmission uids, and
hydraulic oils as well as pour point depressants. In recent years, OCPs have gained market share
from PMAs in engine oils due to their relatively low cost and acceptable performance. PMAs can
also be manufactured with dispersant functionality, which adds another performance attribute to
an already highly versatile additive. The most direct method for preparing dispersant PMAs is to
incorporate a nitrogen- containing monomer into the polymer during copolymerization. Alternately,
various nitrogen-monomer grafting techniques can be used.
TABLE 19.10
Viscosity Modifi ers
VM Name Abbreviation Polymer Structure
Ole n copolymer poly(ethylene/propylene)
(may contain diene termonomer)
OCP Linear copolymer (can contain
long-chain branching)
Polyalkylmethacrylate PMA Linear copolymer
Hydrogenated radial polyisoprene
(can contain styrene as comonomer)
HRI Star polymer
Hydrogenated styrene–isoprene HIS Linear A-B block copolymer
Hydrogenated styrene–butadiene HSB Linear tapered block copolymer
Polyisobutylene PIB Linear homopolymer
Styrene–ester, alternating copolymer
of styrene and alkylmaleate
SE Linear copolymer
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488 Lubricant Additives: Chemistry and Applications
19.6.3 DISPERSANT VISCOSITY MODIFIERS
Various VMs can be prepared with the incorporation of dispersant properties. These dispersant
VMs (dVMs) have been used to provide improved sludge and soot handling performance to engine
oil lubricants. They can either substitute for or add to the existing dispersant in the formulation. As
a replacement for dispersant, they are required to provide equivalent performance. As a top treat to
the existing additive, they will provide a boost in performance especially in areas of sludge and soot
handling. Examples include dPMAs and dOCPs.
19.6.4 SHEAR STABILITY OF ENGINE OILS
Polymeric VMs are susceptible to mechanical and in some cases thermal shearing, leading to a loss
in oil viscosity. The SSI of an engine oil VM is de ned by the following equation. The SSI gives an
indication of the mechanical stability of the VM.
SSI
if
io
⫽
⫺
⫺
⫻
mm
mm
100
where
m
i
= initial viscosity of lubricant with the VM (cSt)
m
f
= nal viscosity of lubricant after shear
*
m
o
= viscosity of lubricant without the VM (cSt)
Numerically, the SSI can be explained as follows: a VM with a low SSI number is more shear stable,
whereas a VM with a high SSI number is less shear stable. The SSI value of the VM will depend on
its molecular weight. Higher-molecular-weight VMs will have the greatest thickening ef ciency for
a given weight of polymer but will have the lowest shear stability (highest SSI). 55 SSI represents
the lowest shear stability acceptable for modern engine oils. Although this is not unusual for North
American PCMO, it is quite uncommon to nd this shear stability being used in Europe where
minimum shear stability is speci ed in the ACEA and OEM speci cations. A VM with 25 SSI
or less is typical for European diesel and gasoline applications, whereas a 35 SSI VM or less is
preferred for North American diesel formulations.
19.6.5 VISCOSITY GRADE
A lubricant’s viscosity grade, which de nes the useful operating temperatures under which it may
be used, is de ned by the number of viscometric measurements that are given in various Society
of Automative Engineers (SAE) speci cations. Polymeric VMs are crucial in allowing many vis-
cosity grades to be made. Most OEMs will use the viscosity grade to de ne the lubricant that best
works in their equipment. For engine oil lubricants, the viscosity grade is de ned by the SAE J300
speci cation.
In general, an OEM will aim to use the lowest viscosity oil possible, to reduce energy losses
due to friction. However, they will usually recommend a minimum oil viscosity with which their
equipment will work comfortably. These limits may not always coincide with the SAE J300
speci cation especially in the case of the high temperature and high shear viscosity. European
OEMs have historically been more conservative and most have speci ed a minimum HTHS
* Note that the SSI value is dependent on the particular shearing device used to measure shear stability. Common devices
include the Kurt Orbahn fuel injector rig, CRC L-38 engine test, sonic shear device, and the KRL tapered bearing rig.
The latter is primarily used to measure the SSI of driveline uids such as highly shear-stable ATF and gear oils.
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Additives for Crankcase Lubricant Applications 489
viscosity of 3.5 cP for their engine oils irrespective of viscosity grade. This limit is still applied by
European heavy-duty diesel OEMs since bearing wear is seen as a critical performance parameter.
This would mean that an SAE 10W-30 oil would not only have to meet the SAE viscosity grade
but also have to be >3.5 cP in the HTHS viscosity test. North American diesel oils are similar to
their European counterparts with 15W-40 making up the majority of the market. However, there
are some 10W-30 oils in use for which there are no HTHS viscosity minimum limits other than that
speci ed in SAE J300.
For some European passenger car OEMs, there has been some relaxation in the OEM limits
applied to the HTHS viscosity as engine designs have changed to accommodate lower-viscosity
oils. Lower-viscosity oils enable improvements in fuel economy to be made. For example, Volkswa-
gen has published oil speci cations VW 503 and 506 for their gasoline and diesel engines. These
specify an SAE 0W-30 with an HTHS from 2.9 to 3.4 cP together with a fuel economy target. The
reduction in HTHS viscosity for PCMO in Europe is moving in line with North America where
most of the gasoline oils are 5W-30s with HTHS limits in line with the SAE J300 speci cation.
In addition to this, some OEMs are now using 5W-20 oils for factory ll to ensure even better fuel
economy. This is important since some VMs have poor temporary viscosity loss performance at
high temperatures. If an HTHS of >3.5 cP is required, then it is easier to formulate this oil with an
OCP. If the HTHS target is <3.5 cP, then most VMs will suf ce.
19.6.6 VISCOSITY MODIFIER REQUIREMENTS
The necessary attributes for polymeric VI improvers are as follows:
Good thickening for cost-effectiveness
Proper shear stability to stay in grade
Temporary shear stability to meet high-temperature, high-shear requirements (especially
where it is speci ed)
Minimum low-temperature viscosity for cold cranking and pumping
Minimal deposits at high temperature, for example, pistons and turbochargers
Correct selection of the VM will allow all the viscometric requirements to be achieved at the
optimum cost. This being done, it is then necessary to evaluate the formulation in various engine
and eld tests. The performance of VM in the engine and service duty requirements will then de ne
whether the VM is suitable for the intended application.
19.7 POUR POINT DEPRESSANTS
All mineral base oils contain some paraf nic components. These have very good viscosity–
temperature dependence, but they are liable to form waxes at lower temperatures. Although the
effective volume of these waxes is low, they can still form a network of wax crystals that prevents
the oil from owing. One way to investigate this phenomenon is to measure an oil’s ability to ow
at low temperatures by way of its pour point. The pour point temperature of an oil is de ned as the
lowest temperature at which the oil is still capable of owing and is measured according to ASTM
D-97. Additives used to reduce the pour point temperature may also bene t the low-temperature
pumping viscosity.
Pour point depressants work at low temperatures, not by preventing the formation of wax crys-
tals, but by minimizing the formation of wax networks and thereby reducing the amount of oil
bound up in the network. Examples of pour point depressants include polyalkylmethacrylates, sty-
rene–ester polymers, alkylated naphthalenes, ethylene vinyl acetate copolymers, and polyfuma-
rates. Treat rates are typically <0.5% (Figure 19.32).
•
•
•
•
•
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490 Lubricant Additives: Chemistry and Applications
19.8 FOAM INHIBITORS/ANTIFOAMS
Entrained gas or foaming of a lubricant will reduce its effectiveness and needs to be minimized
and at best stopped from building up during engine operation. In engine oils, the presence of foams
can result in reduced oil pressure leading to engine damage particularly for hydraulic lash adjusters
or for hydraulically actuated unit injectors. Air entrainment is another problem. This may lead to
cavitation of the oil lm in bearings and possible failure. The performance of hydraulically actuated
unit injectors is also sensitive to the amount of entrained air.
For simple oil formulations, a foam inhibitor may not be necessary. However, the stability of
foams increases as more additives are added to the lubricant. This has necessitated the use of foam
inhibitors such as those listed as follows:
Dimethylsiloxane polymers
Alkylmethacrylate copolymers
Alkylacrylate copolymers
These compounds are borderline soluble in the lubricant and function by reducing the surface ten-
sion at the interface of the air bubble, thus allowing the bubble to burst more easily. To function
effectively, they must be present as a ne dispersion.
Foam inhibitors are usually added to the lubricant at very low levels typically <20 ppm. At
higher levels, the solubility becomes an issue and is noticeable by an increase in the cloudiness of
the lubricant and possible drop out of the foam inhibitor.
Foaming is measured according to ASTM D-892, which uses air owing through a porous ball
to create foam in the test oil sample. The amount of foam and its stability are measured at 24 and
94°C. ASTM D-6082A is a variation of this test but measures foaming at 150°C. Additional engine
tests such as the Navistar HEUI have also been introduced for diesel oils since API CG-4. This test
measures a diesel oil’s ability to minimize air entrainment that could affect the performance of unit
injectors, which are hydraulically actuated. Gamma ray detection techniques are also used to moni-
tor the entrained air in an engine by way of the oil density. This method is used by BMW for their
oil approval system.
REFERENCES
1. Klamann, D., Lubricants and Related Products, Verlag Chemie, Hamburg, 1984.
2. Mortier, R.M. and Orszulik, S.T., eds., Chemistry and Technology of Lubricants, Blackie Academic &
Professional, London, 1997.
3. Smalheer, C.V. and Smith, R.K., Lubricant Additives, The Lezius-Hiles Co., Cleveland, OH, 1967.
4. Gergel, W.C., Detergents: what are they? The JSLE/ASLE Meeting, Tokyo, Japan, June 10, 1975 (and
references therein).
5. Kreuz, K.L., Gasoline engine chemistry as applied to lubricant problems, Lubrication, 55, 53–64,
1969.
6. Kreuz, K.L., Diesel engine chemistry as applied to lubricant problems, Lubrication, 56, 77–88, 1970.
•
•
•
CH
2
C
CH
3
COOR
Paraffin
Polyalkylmethacrylat
e
Alkylated wax naphthalene
FIGURE 19.32 Examples of pour point depressants.
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Additives for Crankcase Lubricant Applications 491
7. Roby, S. et al., Lub. Eng., 50(12), 989–955.
8. Harrison, P.G., Brown, P. and McManus, J., Wear, 156, 345–349, 1992.
9. Inoue, K. and Watanabe, H., ASLE Trans., 26, 189–199, 1983.
10. Asseff, P.A., US Patent 2,261,047, October 28, 1941, assigned to Lubrizol.
11. Freuler, H.C., US Patent 2,364,283, December 5, 1944, assigned to Union Oil Co.
12. Schreiber, W., US Patent 2,370,080, February 20, 1945, assigned to Atlantic Re ning Co.
13. Jones, R. and Coy, R.C., ASLE Trans., 24(1), 77–90.
14. So, H. and Lin, Y.C., Wear, 177, 1994, 105–115.
15. Papey, A.G., Lub. Sci., 10(3), 1998.
16. Georges, J.M. et al., 53rd Annual Meeting of STLE, Detroit, MI, May 17–21, 1998.
17. Willermet, P.A. et al., Tribol. Int., 28, 163–175, 1995.
18. Eberan-Eberhost, C. et al., Ash-forming extreme pressure/anti-wear lubricant additives, Paper presented
at the seminar “Additives for Lubricants,” TAE, Esslingen, Gremany, December 11–13, 1991.
19. Habeeb, J.J. and Stover, W.H., ASLE Trans., 30(4), 419–426.
20. Korcek, S. et al., SAE 810014.
21. Jones, R. and Coy, R.C., ASLE Trans., 24(1), 91–97.
22. Kawanura, M. et al., SAE 852076.
23. Ingold, K.U., Inhibition of autoxidation of organic substances in liquid phase, 61, 563–589, 1966.
24. Johnson, D., Korcek, S. and Zinbo, M., Inhibition of oxidation by ZDTP and ashless antioxidants in
the presence of hydroperoxides at 160°C, Fuels and Lubricants Meeting, San Francisco, CA, October
31–November 3, 1983, pp. 71–81.
25. Rasberger, M., Oxidative Degradation and Stabilisation of Mineral Oil based Lubricants, R.M. Mortier
and S.T. Orszulik, eds., VCH Publishers, Inc., New York, 1992, Chapter 4, pp. 83–123.
26. Abou El Naga, H.H. and Salem, A.E.M., Effect of worn metals on the oxidation of lubricating oils, 96,
267–283, 1984.
27. Ingold, K.U., J. Phys. Chem., 64, 1636, 1960.
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493
20
Additives for Industrial
Lubricant Applications
Leslie R. Rudnick
CONTENTS
20.1 Introduction ....................................................................................................................... 493
20.2 History of Additives ..........................................................................................................494
20.3 The Function of Additives .................................................................................................496
20.4 Classes of Additives ..........................................................................................................498
20.4.1 Antioxidants ........................................................................................................498
20.4.2 Antiwear and Extreme-Pressure (Antiscuf ng) Additives .................................499
20.4.3 Friction Modi ers ...............................................................................................499
20.4.4 Viscosity Modi ers/Viscosity Index Improvers .................................................499
20.4.5 Tackiness and Antimisting Additives .................................................................500
20.4.6 Seal Swell Additives ...........................................................................................500
20.5 Dyes ...................................................................................................................................500
20.6 Biocides .............................................................................................................................500
20.7 Surfactants .........................................................................................................................500
20.8 Corrosion Inhibitors ..........................................................................................................500
20.9 Additives for Food-Grade Lubricants ............................................................................... 501
20.10 Magnetic Disk Drive Additives ......................................................................................... 501
20.11 Additives for Grease .......................................................................................................... 501
20.12 Additives Used in Biodegradable Lubricants .................................................................... 501
20.13 Additive Chemistry ........................................................................................................... 501
20.14 Industrial Applications ......................................................................................................504
20.15 Summary and Conclusions ................................................................................................506
Acknowledgment ...........................................................................................................................506
References ......................................................................................................................................507
20.1 INTRODUCTION
The objective of this chapter is to provide a review of additives and additive chemistry speci cally
for industrial lubricant applications. This chapter reviews the history of additives and some types
of additives used to improve performance of lubricants in industrial applications. This chapter also
describes the chemistry and mechanisms of action of these additives and some of the important test
methods used to evaluate formulated oils.
An additive is a chemical substance added to a lubricant to improve its properties and per-
formance. Additives can function by physical and chemical interactions. Some additives remain
essentially unchanged as a lubricant is used and others are depleted during use. Still others must
chemically change to perform the desired function. Additives are used widely in many of the
largest industries including the food, soap and detergent, pharmaceutical, paint, plastics, fuel, and
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